A mudaraba contract

Q: Every month we give our eldest uncle all our salaries. He adds his money to the total amount but part of his money is from ill-gotten gain and was earned in an unlawful way that is based on Riba (usury). The money we earn is from our hard work and honest livelihood. The total of lawfully earned money that he received throughout eleven years is 400,000 Riyals. My father and my uncle want to break up this partnership and each one will take his share. Is it permissible for me to take my father's share in the form of a piece of land (Part No. 14; Page No. 336) in order to build on it? Is it permissible for me to take a portion in return for my service? It should be taken into consideration that the lawful money is mixed with the unlawful and that I have no documents to prove that I gave him my salary in order to take my right in a legal way.

A: If the case is as you have mentioned, it is permissible for you to take a piece of land or money as long as it is no more than what you have given him. You can resort to the court, if there is dispute. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.